Before being put in a pak file, assets undergo a process called cooking where the data used by the engine is stripped so only the data the game requires to run is in the final pak
You cannot 'decook' content just as you cannot 'decook' a steak once grilled
Cooked assets are not able to be edited in the engine as that data has been stripped however they can be edited through the use of Asset Editors
After editing they can still be put in a mod as these editors should handle binary equality for you